Control for admission to a data network for providing service quality

ABSTRACT

Control for admitting microflows to a data network consisting of allocating logic priority levels to these microflows making it possible to implement a microflow preemption order based on this logic priority. If the service quality required for a new microflow A cannot be ensured by the internal resources of the network, it is thus possible to free the internal resources of said network by preempting a lower logic priority microflow B.

[0001] The present invention concerns control of service quality on adata network. It more specifically applies to data networks allowing thesupply of various services, such as transmission of voice, data, videoetc. This network can for example be a network based on the protocols ofthe TCP/IP (Transport Control Protocol/Internet Protocol) family, thatis the type commonly known as Internet.

[0002] Certain services require an expressed reservation of resourceswithin the network. In fact, certain networks, such as Internet, havebeen provided to transmit data, but neither the voice nor video. Withinthe Internet, the transmissions of data are carried out in the form ofpackets, each packet being routed to its destination independently ofthe other packets. Each packet is traditionally identified by a IPheader, a 5-tuple: protocol used, address, address and transmitter port,address and port of the recipient. The Ip header can include other morespecific data concerning the packet in question(length).

[0003] The term microflow is generally understood to be a set of packetswhich has the same 5-tuple or at least the same 4-tuple. In effect, theIP header is unable to include identification of the port of thetransmitter. In the rest of the description, the term microflow coversthese two possibilities. The term flow is understood to be a set ofpackets or microflows having at least one common parameter of the IPheader.

[0004] So as to transmit the flow of packets corresponding to the voiceor images by means of these networks, it is necessary to reduce the rateof losses of the packets and also the transmission time so as to ensureeffective listening or sufficient viewing for the recipient of thetransmission. This minimization of the loss rate of packets and thetransmission time is normally carried out via the reservation ofinternal resources within the nodes of the network (or routers).

[0005] To sum up, in practice, the terminal wishing to obtain a certainservice quality for a specific flow transmits a service quality requestfor said flow before sending the corresponding packets.

[0006] Generally speaking, the service quality request is a resourcereservation request, for example conforming to the RSVP (Reservationprotocol) as defined by the RFC 2205 of the IETF (Internet EngineeringTask Force).

[0007] According to said RSVP protocol, each router receiving aresources reservation request must initially verify the resources askedfor are available and route the request according to conventionalrouting algorithms. The resources reservation request thus follows apath which shall be normally that of the packets of the flow in questionuntil it reaches the addressee. The latter then sends a reply to theinitial transmitter which will ascend the path via an oppositedirection. During this second passage, each router shall effectivelyreserve the requested resources.

[0008] With this type of protocol, each router needs to ensure themaintenance of the processing context corresponding to the servicequality request which has been asked for. In particular, if a router ofthe network processes four flows, it needs to manage four correspondingstand-by files, that is one per flow.

[0009] The DiffServ (Differentiated Services model) architecture asdefined by the RFC 2475 of the IETF offers a different resourcesreservation mechanism. Said mechanism is based on a priority marking ofthe packets of the IP flows. According to this architecture, the controlof service quality is implemented by the allocation of priorities,called colours in this context, to each packet of a flow. The colouredpackets need to be processed according to their priority by the routerreceiving them. The router no longer has to manage standby files perflow, but only a single standby file. In practice, the priority levelsgenerally correspond to the nature of the flow. A voice traffic musthave the highest priority, known as “expedited forwarding” in theDiffServ architecture, whereas a Web traffic ought to have the lowestprecedence, known as “Best Effort” in the DiffServ architecture.

[0010] In practice, the RSVP or DiffServ solutions are complementary toeach another so that the networks architectures of the prior artgenerally simultaneously implement the two protocols so as to make useof their respective advantages.

[0011] An implementation example of the prior art is shown on FIG. 1. Adescription of said such prior art can be found in the RFC 2998 documententitled “A Framework for Integrated Services Operation over DiffServnetworks”.

[0012] The data network N comprises the routers R₁, R₂, R₃, R₄, R₅, R₆.Some of these routers are Edge routers R₁, R₂, R₃, that is they areequipped with means for communicating with terminals, office-basedapplications or routers outside this data network N. The other routersR₄, R₅, R₆ are internal routers which only have means for communicationwith other internal routers of the data network N.

[0013] In addition to the edge routers, the network may comprise othertypes of edge equipment. For example, this equipment may be gatewayswhose function is to transmit and arrange without having to carry out IProuting (Internet protocol).

[0014] According to this prior art, the edge equipment (routers,gateways, etc) are able to use the RSVP protocol, whereas the internalrouters mainly use the DiffServ mechanism. But it is also possible tohave certain internal routers which use the RSVP protocol, only a corenetwork implementing the DiffServ protocol. It is also possible to have“All” DiffServ networks.

[0015] In the network shown on FIG. 1, if a terminal T₁ initiates a flowrequiring a certain service quality, with the terminal T₃, for example avocal communication which requires, apart from other things, a minimumtransmission period, it sends a resources reservation request accordingto the RSVP protocol. This resources reservation request is received andthen processed by the edge equipment R₁. The latter then checks to seeif there are effectively the required internal resources (especially thepassband) so as to provide the requested service quality. It also checksin particular that the current aggregation of the flows at its outletmake it possible to accept this new flow.

[0016] If appropriate, the edge equipment R₁ can transmit a reply to theterminal T₁ informing it that the resources reservation has beeneffectively carried out.

[0017] The terminal T₁ then sends the packets of the flow to theaddressee terminal T₃.

[0018] In accordance with the DiffServ mechanism, the router R₁ markseach of the packets of the flow it receives with the precedenceallocated to the flow according to the resources reservation requestpreviously received. This is the “Code Point”.

[0019] The packets are routed inside the data network N via the” routersR₁, R₄, R₅, R₆ and R₃.

[0020] The router R₃ then sends the flow of packets to the terminal T₃and the service quality request according to the RSVP protocol is sentto this terminal T3.

[0021] More generally, each of the routers of the network receives thepackets which may correspond to various flows initiated in the networkN. All these packets are marked with a precedence according to theDiffServ mechanism. Each router processes the packets it receivesaccording to the precedence (such as “Expedited Forwarding”, “BestEffort”) allocated to it.

[0022] This solution of the prior art presents a problem since theverification of the available resources is only carried out by the edgeequipment. If two service quality requests are, for example, initiatedon two separate edge equipment elements, the following may result for aninternal router of the network find it impossible to satisfy therequested service quality. The two service quality requests could begranted when one or even both could not be satisfied. In addition, thenumber of levels of precedence which may be granted according to theDiffServ mechanism is limited. Thus, all the flows corresponding to thevoice traffic shall generally have the same DiffServ precedence andtypically the precedence known as “Expedited Forwarding”. Thus, eachrouter shall process the “voice quality” type packets with the sameprecedence. If a congestion problem occurs to a router receiving severalflows of this type, this shall result in an arbitrary deterioration ofservice quality for at least one of these flows.

[0023] This type of problem is common to all those solutions based on anadmission control carried out by the equipment of the network. This forexample is the case with the solutions described by the European patentapplications EP 0714 192 from the IBM company and the document EP 0398037 of the Toshiba company.

[0024] So as to illustrate this problem, if one looks again at thenetwork N shown on FIG. 1, in the case where the terminal T₂ initiates asecond service quality request from the edge equipment R₂ for a new flowof packets. This second request undergoes the same processing as therequest initiated by the terminal T₁ ands is similarly intended for theterminal T₃.

[0025] This new flow of packets initiated by the terminal T₂ follows apath R₂, R₆, R₅ and R₃ as far as the terminal T₃.

[0026] One portion of this path R₅, R₃ is common with the path borrowedby the flow of packets derived from the terminal T.

[0027] If one considers the case of an inexpensive configuration of thenetwork, the links R₅-R₃ shall have been dimensioned so as to acceptcertain volume of simultaneous communications, a volume which inpractice ought only to be exceeded in certain statistically raresituations.

[0028] Thus, if the sum of the flowrates of the two flows of packetsinitiated by the terminals T₁ and T₂ is greater than the maximumpossible flowrate on the path R₅-R₃, the router R₅ shall not be able tosatisfy the service quality requested by at least one of the terminalsT₁ or T₂ As the two flows allocate the DiffServ “Expedited Forwarding”precedence, these two packet flows shall be downgraded.

[0029] Because of this mechanism, it is possible to have a significantdifference between the service quality asked for by the terminals andaccepted by the network and the one effectively supplied due to acongestion of the traffic at the level of an internal node.

[0030] One solution is having a server which shall carry outcalculations (algorithms) so as to determine congestion inside thenetwork and accept or not accept a new flow request.

[0031] In the present invention, a case is considered where thesenetworks exist with a server of this type able to determine if theacceptance of a new microflow could result in congestion on at least onenode of the network.

[0032] The object of the present invention is then to determine whichmicroflow needs to be stopped or refused inside the network so as toprevent congestion. If a microflow already initiated in the network isstopped, the internal resources are freed which makes it possible toaccept a new microflow. Otherwise, the new microflow is refused.

[0033] According to the invention, a mechanism for allocating a logicpriority to each microflow is implemented by the application requestingservice quality. This logic priority enables each network concerned bytransporting a microflow to implement a microflow preemption logic in anassociated admission controller.

[0034] In this way, it is possible to design data networks cheaply basedon a statistical analysis of the flows to be processed with optimumservice quality management.

[0035] More specifically, the object of the invention concerns anadmission control inside a network having a certain number of edgeequipment elements for receiving the microflows to be transmitted insaid network, said system being characterized in that an applicationrequesting service quality for transmitting a microflow in the networkincludes means for allocating a logic priority to said microflow, saidnetwork including an admission controller comprising means to receive arequest for service quality associated with said microflow to betransmitted and the logic priority which has been allocated to it andmeans to accept or prohibit said microflow.

[0036] The means to accept said microflow include means for determiningan order for the preemption of the microflows in the network accordingto their logic priority so as to free the internal resources of thenetwork with the aim of assessing the service quality requested by saidmicroflow via the lowest logic priority microflow preemption.

[0037] In one embodiment of the invention, the admission controllerassociated with a network determines according to its preemption rulesthe microflow(s) to be preempted and informs the application of this.

[0038] In another embodiment of the invention, the admission controlleris able to collaborate with said application for determining the flowsto be preempted by providing it with a list of microflows which could bepreempted.

[0039] According to the invention, for each network which a microflowwill traverse, the admission controller associated with this network isinformed by the admission controller associated with the precedingnetwork of the logic priority allocated to the microflow.

[0040] Thus, by using an admission controller according to theinvention, a new microflow can be admitted into the network only if theservice quality requested can effectively be satisfied by interrupting,if appropriate, using a preemption mechanism one or the packetmicroflows already initiated in the network and allocated with thelowest logic priority.

[0041] It is therefore possible to avoid any over-supplying of theresources of the data network and obtain inexpensive architectures basedon their statistical use.

[0042] The invention and its advantages are shown hereafter more clearlyin the following description of embodiments with reference to theaccompanying drawings on which:

[0043]FIG. 1, already described, represents a network architecture ofthe prior art using resources reservation mechanisms;

[0044]FIG. 2 illustrates the general principle of an admission controlsystem according to the invention;

[0045]FIG. 3 illustrates a first embodiment example of the invention inan all DiffServ type architecture network

[0046]FIG. 4 illustrates a variant of the admission control mechanismfor this network architecture, and

[0047]FIG. 5 illustrates a second embodiment example of the inventionfor a mixed RSVP/DiffServ type network architecture.

[0048]FIG. 2 diagrammatically represents the admission control principleapplied to a microflow A transmitted by a transmitter, which can be anyterminal, an office-based application, an external router, etc.—to betransmitted via a first data network N₁ and a second data network N₂.Each data network N comprises a set of edge equipment and internalresources (not shown) for transmitting the microflow.

[0049] According to the general principle of the invention, thetransmitter of the microflow A sends a service request Req(A) to anapplication AP. According to the invention, the application allocates itwith a service quality level and a logic priority level. For example,when this concerns a voice transmission originating from a stationidentified as the most important (for example from the Director of acompany), the application AP shall allocate an extremely high level oflogic priority noted *** in the example.

[0050] This application then transmits the service quality request QoS(A), *** and the logic priority which it has allocated to the admissioncontroller AC of the first network. If the admission controller includesmeans for detecting congestion in the network N₁ and if it hascalculated that there will be congestion, it shall either refuse themicroflow A or authorize it but by stopping other microflow(s) alreadyinitiated in the network but allocate with a lower logic priority. Thus,the internal resources are freed by the microflow preemption based onthe logic priorities associated with the microflows.

[0051] Moreover, the admission controller sends the admission controllerAc₂ of the next network N₂ the service quality request and the logicpriority allocated to the microflow.

[0052] Generally speaking, via an admission control system according tothe invention, the logic priority allocated to the microflow istransmitted to each of the admission controllers associated with thenetworks through which the microflow shall pass.

[0053] Preemption means can then be used, if appropriate, in theadmission controller if the latter is able to detect whether theadmission of the new microflow could result in a problem in a node orseveral nodes of the network. In basically dimensioned networks or moregenerally in which it is certain there are no congestion problems, theadmission controller shall simply send the following admissioncontroller the service quality request and the logic priority associatedwith the microflow.

[0054] In the case of a DiffServ type architecture, the microflow isallocated (or is already allocated) with a priority level of the trafficIP called ‘precedence’. For example, a voice traffic is normallyallocated a maximum precedence, namely “Expedited Forwarding”, and a Webtraffic, namely a “Best Effort” low precedence.

[0055] The logic priority allocated by the admission control system ofthe invention makes it possible to allocate to microflows of the sameprecedence a different logic priority permitting the preemption of oneflow on another according to the logic criteria defined in theapplication and not according to the traffic IP.

[0056] For example, the logic priority level added to the microflowscould depend on the identity of the user of the terminal.

[0057] The admission controller of the invention knows the list of flowsinitiated by each of the edge equipment and the logic priority which hasbeen allocated to them.

[0058] Thus, via a knowledge of this information, the admissioncontroller is able to determine as to whether or not the network cansatisfy the new service quality initiated by a terminal.

[0059] In the case where the admission controller carries outcalculations (uses algorithms) to determine whether the current use ofthe network is able to provide the service quality requested for the newmicroflow, the admission controller looks, if appropriate, for the listof lowest logic priority microflows initiated in the network.

[0060] One embodiment example of the invention inside a network with an“All DiffServ” architecture is shown on FIG. 3.

[0061] A transmitter of a new microflow A, namely the terminal T₁ in theexample, sends a service request (1) concerning an application AP whichmay in practice be a call server, an SIP-proxy, an intermediateapplication, a gateway, etc. This request is made according to aprotocol adapted to the application. This protocol can typically be ofthe SIP type (“Session Initiation Protocol”) or even of the H.323 typeof the ITU-T (International Telecommunication Union).

[0062] This application AP is able to carry out formatting, hypothesesof the correlation of several service quality requests, etc.

[0063] According to the invention, this application allocates a logicpriority. In fact, this application has detailed knowledge of themicroflow to be transmitted, especially from the transmitter to therecipient, and not only the from the addresses IP. This application thensends the service quality request (2) with the allocation of a logicpriority, namely in the example a high priority noted *** for the flow Ato the admission controller AC.

[0064] In the example shown on FIG. 3, a microflow B is alreadyinitiated in the network on the edge equipment (router) R₂. Thismicroflow has been allocated by a low logic priority application (notnecessarily by the application AP) noted *.

[0065] Two cases of the figure are shown: in the first case, the networkhas sufficient internal resources to accept the new microflow A, namelywhen it is dimensioned broadly or when the application environment issuch that there is no problem of congestion. In the second case, theacceptance of the microflow A would result in problems of congestion,certainly at at least one node of the network, the admission controllerhaving calculation means enabling it to detect this problem.

[0066] Two variants of a control system according to the invention canthen be used.

[0067] In a first variant shown on FIG. 3, the admission controllerselects from its list of microflows initiated in the network a leastpriority microflow, B in the example, and stops this microflow bysending a corresponding message, Stop B, to the edge equipment which hasinitiated it, R₂ in the example. It sends a message (3) to theapplication to inform it that the flow A has been accepted and whichflows have been preempted. In the example, only the flow B is preempted.

[0068] The admission controller can then send back a message foraccepting the microflow A to the edge router R₁ according to theprotocol COPS. This message contains the normal opening rules (passband,maximum and minimum flows) linked to the precedence of the microflow,for example “Expedited Forwarding”. The router R₁ can then transmit themicroiflow A.

[0069] In a second variant shown on FIG. 4, the admission controllercollaborates with the application AP. It sends (3) this application alist of possible preempted flows. This list may include all themicroflows initiated in the network with a least priority or solely oneportion of them according to predetermined logic rules.

[0070] It is this application AP which then carries out the choice ofpreemption and duly informs (4) the admission controller. The admissioncontroller AC can inform (5) the application the microflow(s) it haseffectively stopped.

[0071] On FIG. 5, another implementation of the invention is shown for amixed RSVP/DiffServ architecture. In this architecture, the terminal T₁sends (1) a service request (SIP or H.323 protocol) to the applicationand sends (2) a resources reservation request according to the RSVPprotocol to the edge equipment T₁. This edge equipment sends (3) thisrequest to the admission controller AC. Moreover, the application APallocates to the microflow A a logic priority, *** in the example,according to the mechanism already described with reference to FIG. 3.It sends (4) the admission controller AC this request and the logicpriority of the microflow A.

[0072] If the admission controller AC receives the resources reservationrequest before receiving the message by the application AP of thecorresponding service quality request, it informs the latter of theresources reservation request (3) and waits in return (4) forconfirmation of the request and the allocation of the priority.

[0073] In all cases, the admission controller of the invention includesmeans to check that the parameters of the resources reservation request(3) clearly correspond to those contained in the service quality requesttransmitted (4) by the application AP. In the case where they do notcorrespond, the admission controller collaborates with the applicationso as to decide whether to accept or downgrade the service qualityrequested (3) by the edge equipment, which is expressed in the openingrules to be applied.

[0074] Next, if a congestion problem needs to be resolved, this can besorted out by the two embodiment variants of the control system of theinvention with reference to FIG. 3 (first variant) and FIG. 4 (secondvariant).

[0075] In the first variant, the admission controller chooses theflow(s) to be preempted according to the logic priority of themicroflows already initiated in the network, stops these flows (Stop B),informs the application AP of this and sends a message accepting themicroflow A to the corresponding edge equipment R₁.

[0076] In the second variant shown on FIG. 5, the admission controllercollaborates with the application AP. It sends (5) this application alist of possible preempted flows. This list may include all themicroflows initiated in the network with a least priority or only oneportion of them according to predetermined logic rules.

[0077] This application AP, which carries out this preemption choice,duly informs (6) the admission controller. In all cases, the admissioncontroller AC informs (7) the application of the microflow(s) it haseffectively stopped. The admission controller then sends the message foraccepting the microflow A, OK A, with opening rules corresponding to theservice quality.

[0078] In this mixed RSVP/DiffServ architecture, the admissioncontroller is able to implement the COPS protocol with the edgeequipment.

[0079] With the admission control system of the invention, the networkis able to accept a microflow requiring a certain level of servicequality (passband, flows) and satisfy it by allowing the freeing of theinternal resources of the network by preempting the microflows accordingto given criteria. For example, a service quality request for a Voicetraffic originating from a transmitter corresponding to an importantcustomer could benefit from a priority higher than a service qualityrequest originating from a third party.

[0080] It is this application which implements the rules for allocatinglogic priorities. These rules are based on the intelligence of theservice in the application.

[0081] In the case where the admission controller of a network has nomeans for detecting a congestion problem or that there are no possiblecongestion problems inside the network, the admission controller has thelogic priority transmitted allocated by the application to the microflowwhich traverses the network.

What is claimed is:
 1. Admission control system in a network having acertain number of edge equipment for receiving microflows to betransmitted inside said network, said system being characterized in thatan application requesting service quality for the transmission of amicroflow in the network includes means for allocating a logic priorityto said microflow, said network including an admission controllercomprising means for receiving a service quality request associated withsaid microflow to be transmitted and the logic priority which has beenallocated to it and means to accept or prohibit said microflow. 2.Control system according to claim 1, wherein the means to accept saidmicroflow include means for determining an order of preemption of themicroflows in the network according to their logic priority so as tofree the internal resources of the network with the aim of providing therequested service quality by said microflow by means of preemption ofmicroflows with the lowest logic priority.
 3. System according to claim1, wherein the admission controller of a network is able to transmitmessages for accepting, prohibiting or stopping microflows to acorresponding edge equipment of said network in accordance with the COPSprotocol.
 4. System according to claim 1, wherein the means fordetermining preemption are able to send the application asking forservice quality a list of flows initiated in the network and allocatedwith a lowest logic priority and to receive from said application aselection of a microflow or microflows to be preempted.
 5. Systemaccording to claim 1, wherein the preemption determination means areable to send the requested service quality application informationindicating the preempted flow(s).
 6. Admission control system accordingto claim 1 and applied to a network comprising edge equipment using theRSVP protocol, wherein the admission controller is able to receive arequest for reserving the resources of said edge equipment.
 7. Systemaccording to claim 6, wherein the admission controller is able toreceive from an edge equipment element a resources reservation requestassociated with a microflow, and wherein the admission controllerincludes means able to inform the application requesting service qualitythat this request is received.
 8. System according to claim 1, whereinthe admission controller associated with a network includes means forinforming one admission controller associated with another network ofthe logic priority allocated to a microflow.